1. Field of the Invention
This invention relates to a rotation-transmitting apparatus, and more particularly to a mechanical rotation-transmitting apparatus for transmitting rotation from a driving unit to a rotating element in a vacuum system.
2. Description of the Related Art
During a process for manufacturing a semiconductor or a photoelectric element, a vacuum chamber in a hollow member is often required for performing a film plating operation. To activate a rotating element in the vacuum chamber, it is necessary to operate a rotation-transmitting apparatus to transmit a rotational power to the rotating element. The rotation-transmitting apparatus primarily includes a mounting member disposed on the hollow member, and a rotating shaft extending through the mounting member. The rotating shaft has an outer end disposed outwardly of both the hollow member and the mounting member and connected to a driving unit, and an inner end extending into the hollow member and connected to the rotating element. The rotating shaft is driven by the driving unit to rotate about a central axis thereof to thereby drive rotation of the rotating element. As such, the rotating shaft is rotatable relative to the mounting member. An airtight seal must be established between the mounting member and the rotating shaft and between the mounting member and the hollow member, such that the vacuum chamber is not in fluid communication with the atmosphere.
To allow the rotating shaft to rotate in an airtight state, a magnetic fluid can be introduced into the rotation-transmitting apparatus such that, during transmission of rotation, no contact and friction occur between the rotating element and the rotating shaft, thereby increasing the service life of the rotation-transmitting apparatus and allowing the rotation-transmitting apparatus to be used with a vacuum system that has a high vacuum level. However, since the magnetic fluid is relatively expensive, it is not worthwhile to use in a vacuum system having a low vacuum level from a cost standpoint. Another rotation-transmitting apparatus is disclosed in Taiwanese Patent No. 247855, and includes O-rings that are used for establishing airtight seals and that are made at a low cost. However, a frictional resistance to rotation of rotatable members of the rotation-transmitting apparatus is increased due to contact between the O-rings and the rotatable members, thereby resulting in an increase in power loss during transmission of rotation. As a consequence, a conventional rotation-transmitting apparatus has a disadvantage of a high cost or a high frictional resistance.